Etching silicon in high aspect ratio features is performed in many semiconductor device manufacturing applications, such as fin trim and lateral recess formation. Plasma etching is a technique known in the art to perform precision etching in semiconductor device manufacturing. However, etching using plasma can result in damage or undesirable modification to underlying layers or structures. Preventing or reducing such damage becomes increasingly important as semiconductor device technology progresses to smaller technology nodes, for example, sub 45-nm nodes. Furthermore, etch selectivity is also important in semiconductor device manufacturing, such as with semiconductor field-effect transistors. Plasma etching typically relies on energetic ion bombardment to provide high etching rates, which makes obtaining etch selectivity difficult.
Accordingly, the inventors have developed improved methods for chemically etching silicon.